Towards an understanding of hole superconductivity

From the very beginning K. Alex M\"uller emphasized that the materials he and George Bednorz discovered in 1986 were $hole$ superconductors. Here I would like to share with him and others what I believe to be $the$ key reason for why high $T_c$ cuprates as well as all other superconductors are hole superconductors, which I only came to understand a few months ago. This paper is dedicated to Alex M\"uller on the occasion of his 90th birthday.Comment: Dedicated to Alex M\"uller on the Occasion of his 90th Birthday. arXiv admin note: text overlap with arXiv:1703.0977

Effect of the coefficient of friction of a running surface on sprint time in a sled-towing exercise

This is an Author's Accepted Manuscript of an article published in Sports Biomechanics, 12(2), 175 - 185, 2013, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/14763141.2012.726638,This study investigated the effect of the coefficient of friction of a running surface on an athlete's sprint time in a sled-towing exercise. The coefficients of friction of four common sports surfaces (a synthetic athletics track, a natural grass rugby pitch, a 3G football pitch, and an artificial grass hockey pitch) were determined from the force required to tow a weighted sled across the surface. Timing gates were then used to measure the 30-m sprint time for six rugby players when towing a sled of varied weight across the surfaces. There were substantial differences between the coefficients of friction for the four surfaces (μ = 0.21–0.58), and in the sled-towing exercise the athlete's 30-m sprint time increased linearly with increasing sled weight. The hockey pitch (which had the lowest coefficient of friction) produced a substantially lower rate of increase in 30-m sprint time, but there were no significant differences between the other surfaces. The results indicate that although an athlete's sprint time in a sled-towing exercise is affected by the coefficient of friction of the surface, the relationship relationship between the athlete's rate of increase in 30-m sprint time and the coefficient of friction is more complex than expected

Ground Rules in Team Projects: Findings from a Prototype System to Support Students

Student team project work in higher education is one of the best ways to develop team working skills at the same time as learning about the subject matter. As today’s students require the freedom to learn at times and places that better match their lifestyles, there is a need for any support for team project work to be also available online. Team working requires that the task roles as well as the maintenance roles are taken into consideration, in that social interactions are just as important as carrying out the tasks of the project. The literature indicates that groupware, whilst effective in supporting the task roles, provides limited support for the maintenance roles of team working in the work place. As groupware was not specifically designed for student team working, it provides limited support for maintenance roles in student team projects. Virtual learning environments similarly provide support for completing the task roles. Many researchers have found that students experience difficulties with their team project work that reduce the perceived benefits of working in a team. It is proposed that helping students to agree on ground rules at the start of a project will improve team cohesion. This paper describes the implementation and evaluation of a prototype system to help students to agree on ground rules as they start their team projects. The system was tested with teams of students carrying out information systems team projects, using an interpretive case study research approach. In this case the teams had the additional problem of being composed of students from across three years of their undergraduate degree programmes, so they did not always have prior knowledge of each other’s preferences. We were trying to establish how useful this software tool would be to these student teams, in starting their project work. The findings showed that some of the student teams did find the ground rules function useful, but the team leaders were the ones who most appreciated its potential. The students may use the outputs in very different ways, but even just looking at the ground rules appeared to get team members thinking about their expectations for team working. Student teams do not often start by thinking about norms, but this study shows a positive benefit of encouraging teams to agree on ground rules at the start of their projects

A Way to the Dark Side of the Universe through Extra Dimensions

As indicated by Einstein's general relativity, matter and geometry are two faces of a single nature. In our point of view, extra dimensions, as a member of the {\em geometry face}, will be treated as a part of the {\em matter face} when they are beyond our poor vision, thereby providing dark energy sources effectively. The geometrical structure and the evolution pattern of extra dimensions therefore may play an important role in cosmology. Various possible impacts of extra dimensions on cosmology are investigated. In one way, the evolution of homogeneous extra dimensions may contribute to dark energy, driving the accelerating expansion of the universe. In the other way, both the energy perturbations in the ordinary three-space, combined with homogeneous extra dimensions, and the inhomogeneities in the extra space may contribute to dark matter. In this paper we wish to sketch the basic idea and show how extra dimensions may lead to the dark side of our universe.Comment: 10 pages, 3 figures. To appear in the proceedings of 2002 International Symposium on Cosmology and Particle Astrophysics (NTU, Taipei, Taiwan), May 31 - June 2, 200